The ‘hybrid’ scenario in JET: towards its validation for ITER

Abstract

In 2003, the performance of the 'hybrid' regime was successfully validated in JET experiments up to βN = 2.8 at low toroidal field (1.7 T), with plasma triangularity and normalized Larmor radius (ρ*) corresponding to identical ASDEX Upgrade discharges. Stationary conditions have been achieved with the fusion figure of merit ( ) reaching 0.42 at q95 = 3.9. The JET discharges show similar MHD, edge and current profile behaviour, when compared with the ASDEX Upgrade. In addition, the JET experiments have extended the hybrid scenario operation at higher toroidal field of 2.4 T and lower ρ* towards the projected ITER values. Using this database, transport and confinement properties are characterized with respect to the standard H-mode regime. Moreover, trace tritium has been injected to assess the diffusion and convective coefficients of the fusion fuel. The maximization of confinement and stability properties provides, to this scenario, a good probability of achieving a high fusion gain at reduced plasma current for durations of up to 2000 s in ITER.